core: remove @effect/language-service plugin and optimize hot path type performance

- Removed @effect/language-service from both packages/core and packages/opencode tsconfig files and dependencies

- Wrapped mergeDeep calls in config loading and LLM streaming to avoid expensive remeda conditional merge type instantiations in hot paths

- Narrowed Drizzle migrate() overload signature to avoid expensive variance checks during database initialization

These changes reduce TypeScript type-checking overhead and improve startup and runtime performance for config loading, LLM streaming, and database migrations.

packages/opencode/src/session/llm.ts

@@ -3,7 +3,7 @@ import * as Log from "@opencode-ai/core/util/log"
 import { Context, Effect, Layer, Record } from "effect"
 import * as Stream from "effect/Stream"
 import { streamText, wrapLanguageModel, type ModelMessage, type Tool, tool, jsonSchema } from "ai"
-import { mergeDeep, pipe } from "remeda"
+import { mergeDeep } from "remeda"
 import { GitLabWorkflowLanguageModel } from "gitlab-ai-provider"
 import { ProviderTransform } from "@/provider/transform"
 import { Config } from "@/config/config"
@@ -29,6 +29,10 @@ const log = Log.create({ service: "llm" })
 export const OUTPUT_TOKEN_MAX = ProviderTransform.OUTPUT_TOKEN_MAX
 type Result = Awaited<ReturnType<typeof streamText>>
 
+// Avoid re-instantiating remeda's deep merge types in this hot LLM path; the runtime behavior is still mergeDeep.
+const mergeOptions = (target: Record<string, any>, source: Record<string, any> | undefined): Record<string, any> =>
+  mergeDeep(target, source ?? {}) as Record<string, any>
+
 export type StreamInput = {
   user: MessageV2.User
   sessionID: string
@@ -134,11 +138,9 @@ const live: Layer.Layer<
             sessionID: input.sessionID,
             providerOptions: item.options,
           })
-      const options: Record<string, any> = pipe(
-        base,
-        mergeDeep(input.model.options),
-        mergeDeep(input.agent.options),
-        mergeDeep(variant),
+      const options = mergeOptions(
+        mergeOptions(mergeOptions(base, input.model.options), input.agent.options),
+        variant,
       )
       if (isOpenaiOauth) {
         options.instructions = system.join("\n")